Recently, rapid advances have been made in both the fields of data communications and computer technology. The increase of the level of technology in these fields has equipped many offices and homes with personal computers and facsimile devices. Additionally, the personal computer is, in many cases, not a stand-alone device but is connected to various private or commercial data bases utilizing the telephone lines for communication. In many instances, single dedicated lines are needed to connect the personal computer, facsimile or similar devices as well as the telephone handset to the telephone communications equipment for transferring data or other information between the home or the office and the outside world. While each system would work perfectly well utilizing its own dedicated line, such a system, especially in the context of a home or small business environment, can be expensive, since each device must be connected to its own dedicated telephone line.
Consequently, devices have been developed in which a single telephone line is utilized as an input device for a personal computer or an input device for a facsimile machine as well as serving its primary function as a communication line to a telephone. One such device is described in U.S. Pat. 4,367,374, issued to Serrano. This patent describes an interface circuit used with a modem to transmit information through or from a standard telephone line. Additionally, this circuit can be utilized to ensure operation of the telephone in its normal manner. Various switches are associated with the interface circuit to ensure that either the system is operating in the telephone mode, or the system is operating utilizing the modem and a computer terminal. In both situations, provision is made for "locking-out" the portion of the system which is not being utilized at that time. However, no provision is made in the patent to Serrano for including a display circuit which visually displays the status of the interface circuit based upon the actual operational status of the circuit. Furthermore, the particular interface circuit of the Serrano patent is not directly connected to the telephone line and both devices which utilize the telephone line for communication. Additionally, no provision is made for switching the circuit from one mode to the second mode when the circuit is actually operating in the first mode.
Consequently, a device must be developed which addresses the deficiencies of the prior art.